* Quake was centred in Ibaraki Prefecture, just northeast of Tokyo
* No sign of irregularities at Fukushima, Tokai Daini nuclear plants
An earthquake with preliminary magnitude of 5.5 shook eastern Japan, including the capital Tokyo, on Sunday morning, but there were no immediate reports of damage and no irregularities at the wrecked Fukushima nuclear power plant.
The earthquake was centred in southwest Ibaraki Prefecture, just northeast of Tokyo. There was no threat of a tsunami.
Tokyo Electric Power Co, operator of the Fukushima nuclear plant 220 km (130 miles) northeast of Tokyo, said there was no apparent impact from the quake.
"We have so far seen no abnormalities in monitoring post figures around the plants or in other parametres," a Tokyo Electric spokesman said.
The Tohoku Shinkansen bullet trains connecting Tokyo with northern Japan were briefly suspended, while Tokyo's two international airports were operating normally and there were no reports of irregularities at the Tokai Daini nuclear facility, public broadcaster NHK said.